The SCFAs are produced by bacteria in the gut during fermentation of insoluble fibre from dietary plant matter.

These have been linked to health promoting effects, including a reduced risk of inflammatory diseases, diabetes and cardiovascular disease.

The researchers analysed the typical daily diet of 153 adults who either ate everything or were vegetarians or vegans.

Most (88 percent) of the vegans, almost two thirds of the vegetarians (65 percent) and around a third (30 percent) of the omnivores consistently ate a predominantly Mediterranean diet.

Higher levels of SCFA were found in all of those who consistently followed a Mediterranean diet.

Levels of SCFAs were also strongly associated with the quantity of fruit, vegetables, legumes and fibre habitually consumed.

The SCFA levels can naturally vary as a result of age and gender.

But researchers suggest that the Mediterranean diet does seem to be associated with the production of health-promoting SCFAs.

“We provide tangible evidence of the impact of a healthy diet and a Mediterranean dietary pattern on gut microbiota and on the beneficial regulation of microbial metabolism towards health maintenance in the host,” the authors wrote in a paper appeared in the journal Gut.

“Western omnivore diets are not necessarily detrimental when a certain consumption level of (plant) foods is included,” they concluded.